There have been many attempts to replace prior art electromechanical torque receiver drivers with modern solid state electronics. Most of the schemes are bulky, wasteful in power consumption, and not cost competitive with the electromechanical parts they try to replace.
In general there are basically two types of solid state synchro torque receiver drivers; open and closed loop types. Of the open loop types the tapped transformer method is considered to be the classic solid state approach. In this approach saturated transistors are used to switch ratiometric voltages from various transfer taps directly to the synchro torque receiver stators. This scheme works very well where low resolution and accuracy can be tolerated, e.g. 36.degree. increments representing numeric wheel positions (0, 1, 2, . . . 9). When higher resolutions are required the number of taps and the number of switching transistors become prohibitive. In addition, accuracy is seriously compromised.
Of the closed loop variety the classic method of driving the synchro stator loads is to generate ratiometric reference voltages representing the desired rotor position and via a feedback system force the outputs to follow the input references. In the classic approach cost and bulky high current, high voltage power supplies are used to power conventional feedback power supplies.
The present invention emulates an electromechanical synchro driver and belongs to the closed loop class. Its major novel advantage is that it draws its power directly from the raw AC.